Fixed-wing aircraft typically include flaps mounted on the trailing edges of the wings. When extended, the flaps modify the effective contour of the wings and, thus, modify the lift characteristics of the wings. During takeoff, the flaps may be extended (at least partially) to shorten the length of runway required to achieve liftoff. During landing, the flaps may be extended (e.g., fully) to slow airspeed and decrease the length of runway required to achieve a complete stop.
The flaps on the wing of an aircraft, particularly the in-board flaps, are typically actuated by a flap carriage mechanism housed within the fuselage (or within the fuselage/wing fairing). A torque tube extends through the fuselage (or though the fuselage/wing fairing) to couple the internal flap carriage mechanism with the external flap. Therefore, an opening must be formed in the fuselage (or in the fuselage/wing fairing) to accommodate movement of the torque tube as it urges the corresponding flap from a retracted position to an extended position, and vice versa.
The torque tube openings on an aircraft, if left unsealed, have been known to affect aircraft aerodynamics. For example, pilots operating aircraft without means for sealing the torque tube openings have experienced vibrations during landing, which are now known to be caused by the unsealed torque tube openings. Therefore, various attempts have been made to seal torque tube openings in aircraft.
Despite advances already made, those skilled in the art continue with research and development efforts in the field of aircraft wing flap actuation.